The present invention relates generally to a digital recording apparatus, and relates more particularly to technology improving the efficiency of a recovery process resolving inconsistencies in AV data and AV data management information left on the disc when the power supply is unexpectedly interrupted.
Digital recorders for recording television programs, movies, and other types of high volume moving picture content to hard disk drive (HDD), Digital Versatile Disc (DVD), and more recently Blu-ray Disc (BD) media are now widely available.
In addition to recording MPEG-encoded AV data, for example, such digital recorders also record management information for the AV data to the digital recording medium. This management information typically includes the title, recording date, aspect ratio, and AV data stream information (data size, time table, frame information) for the AV data content.
One object of conventional digital recorders using optical discs, magneto-optical discs, and other digital media has been to shorten the required processing time when recorder power is turned on and off, and when a disc is loaded and ejected (see Japanese Patent Laid-Open Publication (kokai) 2002-260368).
The device taught in Kokai 2002-260368 segments the recording area into multiple zones, and records the management information to an AV management area in either the zone where the magnetic recording head is currently positioned or in an adjacent zone. The address of the area where the management information is recorded is also stored to nonvolatile memory incorporated in the disc cartridge, and when drive power is turned on or a disc is loaded, the disc recorder reads the management information by referencing the address stored to this nonvolatile memory.
This shortens the seek time of the magnetic head when writing the management information, and shortens the processing time required when the power turns on and off and when a disc is loaded and ejected.
The object of this related art is thus to shorten the magnetic head seek time when reading and writing management information when the power turns on or off and when a disc is loaded or ejected, and the management information is written to the digital recording medium only when drive power is intentionally turned off or the disc is ejected.
If the power supply is interrupted during recording due to a power failure or the power cord being accidentally unplugged, however, management information for the recorded data is not written to the recording medium. This unrecorded management information is thus lost and cannot be recorded when the power supply is restored. An inconsistency between the management information on the disc and the recorded AV data thus results when the power supply is returned, and a recovery process for rectifying this inconsistency is needed.
Two basic methods are available for correcting inconsistencies between the AV data and management information during the recovery process: interpolating the lost management information according to the AV data left on disc, and deleting the AV data to match the management information left on disc. The former method involves analyzing the AV data and interpolating the management information based on the analysis, and therefore requires analyzing the AV data. The problem with the latter method is that only the management information written to the recording medium the last time the disc was normally ejected or the power was normally turned off remains on the disc, and all management information relating to the AV data recorded until just before the power supply failed or was interrupted is lost as a result of the sudden power interruption. All AV data for the program or content recorded until just before the power supply was unexpectedly interrupted must therefore be erased.
Furthermore, while real-time processing is not necessary to recover and record directory information for regular data, the management information recovery and recording process for AV data must run in real time. This is because if a head seek occurs while recording AV data and the recovery data is recorded to a different area, and the head then returns to the original location to continue recording the next AV data block, AV data must be buffered to memory for a period equal to the time needed for the two seek operations and recording the recovered data, but if a buffer of sufficient size to store the AV data during this time is provided, product cost rises accordingly.
An object of the present invention is therefore to provide a digital recording apparatus that can efficiently complete a recovery process for fixing inconsistencies between the AV data and management information left on the disc when the power supply is unexpectedly interrupted during recording, such as when a power failure occurs or the power cord is accidentally unplugged.